Multitech MMH900, User Manual

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Appendix J - Internal MMH2834 Composite Link Modem Commands
Async/Sync This command can be used to set the on-line mode to either
Mode synchronous or asynchronous. AT&M0 will set the MMN2834
Switching to Asynchronous mode, and all communications will be
&M Asynchronous, in both On-line and Command modes. AT&M1
causes the MMH2834 to communicate asynchronously when in
Command mode and switch to synchronous mode while on-line.
The modem defaults to &M0 (asynchronous communications)
on reset or power-up.
Synchronous The &X command selects the Synchronous Transmit Clock
Transmit Clock Source in conjunction with the MuxClock ($MUXCL) command
Select for the composite link. External clocking is the default condition.
&X External clocking is when the DTE provides transmit clocking to
the modem on pin 24 of the RS232C interface.
&X0 is the default setting which is internal clocking. Internal
clocking is when the modem provides transmit clock to the DTE
on pin 15 of the RS232C/V.24 interface. The &X1 command
selects External clocking. &X2 enables Slave Clocking. The
&X2 Command causes the MMH2834 to generate the transmit
clock timing (pin 15) from the receive clock (pin 17) from the DTE
(therefore 15 and 17 are the same). In this mode (Slave
Clocking), all timing is controlled by the receive clock.